java - What's the difference between "(ex1)|(ex2)|(ex3)" and "[(ex1)(ex2)(ex3)]" -

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i'm trying create general code ease usage of regexes, , thinking how implement or function.

the title pretty accurate (ex1,ex2,ex3 regular expressions). not considering grouping, what's difference between:

"(ex1)|(ex2)|(ex3)"

and 

"[(ex1)(ex2)(ex3)]"

these both should or relation between named regexes, might missing something. way 1 more efficient other?

(ex1)|(ex2)|(ex3)

here capturing ex1, ex2 , ex3.

here:

[(ex1)(ex2)(ex3)]

( , ) quoted , treated since they're enclosed in [ , ] (character classes), matches (, ), e, x, 1, 2 , 3.

note it's equivalent (the order not important):

[ex123)(]

important notes on character sets:

the caret (^) , hyphen (-) can included is. if want include hyphen, should place in beginning of character class. if want match caret part of character set, should not put first character:

  • [^]x] matches that's not ] , x []^x] matches ], ^ or x
  • [a-z] matches letters a z [-az] matches -, a , z

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